Salicylic Acid in the Mitigation of Salinity Stress in Early Dwarf Cashew: Cellular Damage, Physiological Indices, and Growth

The aim of study was to investigate the effects of foliar application of salicylic acid on cellular damage, physiological indices, and growth of dwarf cashew cultivated under salt stress. A 5 × 4 factorial scheme, resulting from the combination of five ECiw levels (0.4, 1.2, 2.0, 2.8, and 3.6 dS m−1) and four salicylic acid concentrations (control—0, 1, 2, and 3 mM), with three replications. Irrigation water salinity of 3.6 dS m−1 inhibited the synthesis of photosynthetic pigments, gas exchange, chlorophyll a fluorescence, and the growth of dwarf cashew plants. Foliar application of salicylic acid at concentrations ranging from 0.1 to 2.5 mM mitigated the effects of salt stress on relative water content, stomatal conductance, internal CO2 concentration, CO2 assimilation rate, instantaneous carboxylation efficiency, variable fluorescence, quantum efficiency of photosystem II, stem diameter at the grafting point, and plant height, while also reducing electrolyte leakage and initial fluorescence in dwarf cashew plants at 180 days after transplanting. Salicylic acid (SA), when applied at appropriate concentrations, alleviates the deleterious effects of salt stress on the growth and physiological performance of dwarf cashew plants.